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ESTCube-1 student satellite in-orbit experience and lessons learned
10th IAA Symposium on Small Satellites for Earth Observation
Berlin, Germany Andris Slavinskis et al.
23.04.2015
Electric solar wind sail (E-sail) Propellantless propulsion system Charged long thin tethers Charged particles in the solar wind Invented by Pekka Janhunen (FMI) Record fast transportation in
Solar System Enables new missions Spin-off: plasma brake
for deorbiting Has to be tested!
ESTCube-1 overview Project started in 2008 First E-sail in-orbit experiment 10-metre tether interacts with ionospheric plasma Subsystems
Attitude control to spin up satellite
Payload to deploy tether Camera to
image tether end-mass Attitude determination to
measure E-sail force Electrical power system Command and data handling system Communication system Structure
In-orbit experience In August 2012 schedule was accelerated by moving
delivery date from May to January, 2013 Launched on May 7, 2013 on board Vega Successful early operations Software updates
Power saving methods and modes (EPS, CDHS, CAM) Timed beacon function (EPS) Data logging functions (EPS, CDHS, ADCS) Stability updates/bug fixes (EPS, CDHS, ADCS) ADCS software (runs on CDHS) Histogram analysis (CAM) Experiment-related functions (EPS, CDHS, ADCS)
First image on May 15 In total more than 270 images
First image
Histogram analysis: before
Histogram analysis: after
Many other images
In-orbit experience Purposes of images
Characterise camera: white balance, degradation of optics, hot pixels
Provide independent source of attitude to validate ADCS: accuracy better than 2°
Public outreach: media, facebook, presentations
In-orbit calibration of ADCS In-orbit results differ from laboratory calibration Statistical methods On-board images Kalman Filter output
In-orbit experience Problems with unwanted internal
magnetic field Ferromagnetic bolts and battery casings Magnetic moment larger than coils can produce Satellite follows geomagnetic field and spins
around internal magnetic field vector Tests with engineering model and Helmholtz coils
Characterisation of internal magnetic field and coil correction matrix
Detumbling: successful Pointing: (mostly)
impossible Spin up: partly
successful and suitable
Secondary mission objective
Experiment In September 2014 attempts were made to deploy
tether Tether deployment has not been confirmed by
camera nor angular velocity measurements Attempts to measure reel (not) turning Probably tether reel is not turning Failed reel lock deployment or Motor is jammed Attempts to provide different centrifugal forces with
attitude control Spin rate of 840 degrees per second
Spin control
Lessons learned Cover glass
Faster than expected power production deterioration
Attitude sensor laboratory calibration Need to recalibrate attitude determination sensors in
orbit
Unwanted magnetic field Ferromagnetic materials used on-board aligning the
satellite with the geomagnetic field
Payload testing and diagnostics Inability to deploy the tether made it impossible to
measure the E-sail force
Schedule System engineering
Lessons learned Rest of the satellite
Worked as expected and required little in-orbit improvements
Redundancy Failed gyroscopic sensor and internal flash memory
device had redundant counterparts
Engineering research journal articles Pre-launch tests and simulations of all subsystems (8
articles) Post-launch ADCS, EPS, CAM and lessons learned (5)
Leader Technical advisors Start-ups Educational impact
Conclusions Fly early & fly often Be honest COTS: cost-efficiency and redundancy System engineering Technical advisory Magnetic cleanliness Calibration Plasma brake
Small, scalable and efficient deorbiting technology
[email protected] — fb.com/estcube — estcube.eu
Full list of authors: Andris Slavinskis, Mihkel Pajusalu, Henri Kuuste, Erik Ilbis, Tõnis Eenmäe, Indrek Sünter, Kaspars Laizans, Hendrik Ehrpais, Paul Liias, Erik Kulu, Jaan Viru, Jaanus Kalde, Urmas Kvell, Johan Kütt, Karlis Zalite, Karoli Kahn, Silver Lätt, Jouni Envall, Petri Toivanen, Jouni Polkko, Pekka Janhunen, Roland Rosta, Taneli Kalvas, Riho Vendt, Viljo Allik, Mart Noorma
